Prompt lines duplicate/stack up when resizing window via keyboard shortcut (Cmd+/-) #3179

Description

When resizing the Superset window using keyboard shortcuts (Cmd+Plus / Cmd+Minus to zoom in/out), the zsh prompt lines duplicate and stack up in the terminal. Each zoom keystroke adds another copy of the current path/prompt, so after a few zooms the terminal is filled with repeated prompt lines.

This does not happen in iTerm2, Terminal.app, or other common macOS terminals with the same shell configuration.

Environment

• Superset: 1.4.7
• macOS: 26.4 (25E246), Apple Silicon
• Shell: zsh 5.9
• Theme: Powerlevel10k (default 2-line prompt with `PROMPT_ADD_NEWLINE=true`)

Steps to Reproduce

1. Open Superset with a zsh + Powerlevel10k shell
2. Press `Cmd` + `+` (or `Cmd` + `-`) repeatedly to zoom
3. Observe prompt lines accumulating

Expected Behavior

After resize, only the current prompt should remain visible; previous prompt lines should be cleared as in other terminal emulators.

Actual Behavior

Each resize event adds another copy of the prompt, stacking vertically.

Workarounds Attempted (none worked)

• `POWERLEVEL9K_DISABLE_HOT_RELOAD=true` (already default)
• Overriding `TRAPWINCH() { }` to suppress zsh's prompt redraw on SIGWINCH
• `POWERLEVEL9K_TERM_SHELL_INTEGRATION=true` (OSC 133 shell integration)

This suggests the issue is on the xterm.js / Superset side rather than in zsh's resize handling. It may be related to xterm.js reflow behavior on resize (xtermjs/xterm.js#622).

Additional Notes

The issue is triggered specifically by the keyboard zoom shortcuts. Mouse-based window resizing may or may not trigger it (untested, please confirm).